Circular cross flow in steam generator



Feb. 7, 1967 H. F. MENZEL 3,302,620

CIRCULAR CROSS FLOW IN STEAM GENERATOR Filed NOV. 18, 1963 ooo ,0oooo United States Patent C 3,302,620 ClRCULAR CROSS FLOW 1N STEAM GENERATOR Horst F. Menzel, Poway, Calif., assignor to General Dynamics Corporation, New York, N.Y., a partnership Filed Nov. 18, 1963, Ser. No. 324,434 6 Claims. (Cl. 1227) This invention relates to steam generators. More specifically, the invention relates to steam generators particularly adapted for use in conjunction with high-temperature gas-cooled nuclear reactors.

In nuclear power plants utilizing a circulating gas such as helium to conduct heat away from the reactor core, steam for the operation of a work-producing element of the power plant system is normally obtained by the transfer of heat from the gas to the fluid of a water/ steam system. conventionally, such heat transfer is accomplished in a steam generator.

In such a gas-cooled reactor/generator system, it is frequently desirable that the .gas be caused to make only a single pass through the steam generator before being returned to the reactor. It is therefore important that the greatest possible amount of heat be withdrawn from the gas during the single pass in order that maximum efiiciency be achieved. However, it is also important that there be as little restriction to gas flow as possible in order that work expended in transporting the gas through the system be held to a minimum.

Accordingly, it is the principal object of the present invention to provide an improved steam generator.

Another object of the invention is to provide an improved steam generator capable of achieving an eflicient transfer of heat between a working fluid and a gas making a single pass through the generator.

An additional object of the invention is to provide an improved steam generator capable of providing an efficient withdrawal of heat from a gas in a single pass through the generator without a significant restriction to gas flow.

A further object of the invention .is to provide an improved steam generator which causes a gas to flow in a circular path in making a single pass through the generator.

Other objects and advantages of. the invention will become apparent with reference to the following description and the accompanying drawings.

In the drawings:

FIGURE 1 is an elevational view, partially in section,

of an apparatus showing various of the features of the invention;

FIGURE 2 is a sectional plan view taken along line 22 of FIGURE 1;

FIGURE 3 is a fragmentary sectional plan view taken along line 3-3 of FIGURE 1;

FIGURE 4 is a fragmentary sectional plan view similar to the sectional view of FIGURE 3, but showing an alternate embodiment; and

FIGURE 5 is a fragmentary elevational view, partially in section, showing an alternate construction of a portion of the apparatus.

Very generally, there is illustrated in the drawings a steam generator 11 comprising a containment shell 13 having defined therein an elongated flow chamber 15 of annular cross-section provided with an inlet port 17 near its lower end and an outlet port 19 near its upper end, each of which is located adjacent to, but on opposite sides of, a gas impervious upwardly extending baffle plate 21. Gas entering the chamber 15 through the inlet port 17 is thus caused to flow in a circular path through the chamher to the outlet port 19. A perforated baflle plate 23 is disposed adjacent the inlet port 17 opposite the baffle 21 '"ice to cause uniform distribution of the incoming gases, and a series of tube bundles 25 are circumferentially arranged within the annular chamber in the path of the circulated gas and define conduits for the water or steam to be heated in the generator for later production of work by conversion of heat energy to mechanical energy at another part of the lower plant system.

Thus, the heat generated by the reactor core is transferred to a fluid which in turn expends the heat absorbed in a work producing element of the system.

Though the steam generator of the illustrated embodiment is particularly adapted to be used in conjunction with a gas-cooled nuclear reactor and is described with relation thereto, it should be appreciated that it has other applications and may readily be used with any system utilizing a fluid medium for transfer of heat from a source to the fluid to be heated.

More specifically, the containment shell 13 includes a generally cylindrical side wall 27 closed at its upper end by a top head 29 and at its lower end by a bottom head 31. The top head is generally hemispherical in shape and is provided with a central opening 33 adapted to accept a circulator (not shown) for causing movement of the helium gas. The bottom head is also generally hemispherical in shape and is provided with a central opening 32 through which gas enters and is discharged from the generator by means of concentrically arranged inlet and outlet ducts 34 and 35 respectively.

The annular flow chamber 15 is defined within the shell 13 by an elongated vertically disposed vessel 37 suitably supported, as by brackets 39 extending inwardly from the side walls 27 of the shell, and includes an outer cylinder 41, a concentrically arranged inner cylinder 43 and horizontally positioned upper and lower annular shroud sections 45 and 47. The inner cylinder 43 serves as a conduit 44 for gases which have passed through the flow chamber and has a discharge diffuser 48 of downwardly flaring configuration secured to its lower end to conduct the gas to the central opening 32 in the bottom head 31. The lower edge of the diffuser is spaced from the periphery of the central opening 32 to provide a gap 50, the function of which will become apparent shortly.

The inner surface of the outer cylinder 41 and the outer surface of the inner cylinder 43 are preferably covered with an insulating material (not shown) to reduce heat loss. The vessel 37 is of a somewhat lesser height than the shell 13 and is arranged therein so as to provide ample space above the upper shroud 45 to accommodate headers at the upper ends of the tube bundles, as hereinafter more fully described. In addition, the outer diameter of the vessel is slightly less than the inner diameter of the cylindrical side wall 27 of the shell, thus providing a narrow annular passageway 49 intermediate the adjacent walls of the shell and vessel through which gas may be caused to flow.

Positioned within the annular chamber 15 is the gasimpervious baflie plate 21 which extends upwardly from the upper surface of the lower shroud 47 to the lower surface of the upper shroud 45, in parallel relation to the longitudinal axis of the vessel 37, and which extends laterally between the inner surface of the outer cylinder 41 and the outer surface of the inner cylinder 43. The edges of the baffle plate are suitably attached to the adjacent surfaces of the vessel 37, as by welding, so as to prevent the passage of gas therearound. Hence, gas entering the chamber through the inlet port 17 adjacent one side of the bafile can travel in only one direction, i.e., counterclockwise in the illustrated embodiment (FIGS. 2 and 3), in moving to the outlet port 19, as will be explained in more detail shortly. The baffle plate 21 also acts as insulation between hot incoming gas and cooler A exit gas leaving outlet port 19.

The inlet port 17 is in the form of an opening provided in the lower shroud 47 adjacent the gas-impervious baflle 21 but spaced in a counterclockwise direction therefrom (FIGS. 2 and 3). An S-shaped conduit 51 passes through an opening 52 in the diffuser and connects the inlet port 17 to the inlet duct 34 which extends through the opening 32 at the bottom of the containment shell in concentric relation to the outlet duct 35.

Adjacent the side of the inlet port 17 opposite the bafile 21, i.e., spaced in a counterclockwise direction therefrom, is the perforated distribution bafi'le 23 which is provided with a plurality of orifices 55. The perforated baflie is coextensive with the gas-impervious baffle 21 and, like the latter, is arranged in parallel relation to the longitudinal axis of the annular chamber 15. Accordingly, the inlet port 17 is bordered on opposite sides by the impervious and perforated baffles 21 and 23 respectively which thereby define a Vertical passageway 56 through which the incoming gases are conducted upwardly. However, because of the perforated nature of the bafile 23, these upwardly conveyed gases will flow into the chamber through the orifices 55 and thus enter the chamber at various heights so as to provide for a more uniformly distributed flow of gas. If desired, the orifices 55 can be made with varying flow areas in order to insure uniform gas flow through all portions of the bafiie 23. In this respect, since the pressure of the incoming gas will gradually decrease in ascending the vertical inlet passageway '56 as part of the gas passes through orifices 55, the area of the orifices near the lower shroud 47 would be made smaller than the area of the orifices near the upper shroud 45.

The outlet port 19 is in the form of an opening provided in the upper shroud 45 adjacent the gas-impervious baffle 21 and spaced in a clockwise direction therefrom (FIGS. 2 and 3) so as to be located on the opposite side of the 'baflle 21 from the inlet port 17. As shown by the arrows in FIGURES 2 and 3, the gas enters the annular flow chamber 15 through the inlet port 17 and is carried upwardly through the inlet passageway 56. The gas then flows through the orifices 55 of the baffle 23 into the chamber 15 and follows a circular path to the outlet port 19. It will be appreciated that as the gas follows such a path, it is caused to pass through the entire chamber wherein the tube bundles 25 are disposed, thus providing for efficient heat exchange from the gas to the water or steam contained within the tube bundles. However, the path of the gas is not so irregular or devious as would cause a substantial pressure drop within the generator. Due to the uniform gas distribution in the chamber 15 caused by the bafile 23, the gas flow in the chamber is essentially circular until the gas has passed the last of the tube bundles 25.

After passing through the outlet port 19, the gas flows into the space defined by the top head 29 of the containment shell 13 and then is divided into two unequal masses, the larger of which flows downwardly through the conduit 44 defined by the inner cylinder 43 of the vessel 37 to and through the discharge diffuser 48. The smaller portion of the mass of gas from the outlet port 19 flows downwardly from the space defined by the top head 29 through the narrow annular passageway 49 intermediate the side walls 27 of the shell 13 and the outer surface of the wall 41 of the vessel 37. This downwardly flowing mass flows into the space defined by the bottom head 31 and then through the gap 50 to the outlet duct 35 where it re-combines with the larger mass of gas flowing through the conduit 44 and diffuser 48. The action of the gas flowing through the narrow annular passageway cools the side wall 27 of the containment shell 13 and, in addition, tends to equalize the pressure on opposite sides of the outer cylinder 41 of the vessel 37.

The water/ steam system of the steam generator comprises a set of four of the tube bundles 25, each of which includes a plurality of tubes 61 formed into a U-shape so as to provide vertically disposed parallel tubular sections 63, pairs of which are connected at their lower ends by return bends 65. All of the tubular sections 63 of the various tubes 61 of each bundle are connected at their upper ends by a cylindrical horizontally disposed distribution header 69. Periodically spaced horizontally disposed bafiles 67 maintain the tubes in spaced relation to one another in a rectangular horizontal cross-sectional pattern, and a vertically disposed baffle 68 is disposed on each of a pair of opposite sides of the bundles in generally parallel relation to the side walls of the vessel 37.

The tubes 61 extend through holes provided in the upper shroud 45 with the headers 69 located above the shroud and the greater portion of the tubes below the shroud. The four bundles which the tubes form are circumferentially arranged within the annular chamber 15 in the space outside of the vertical passageway 56 defined by the baffies 21 and 23. Each of the set of tube bundles is connected to a different portion of the water/ steam system, as hereinafter described.

It should be appreciated that as the gas travels in a counterclockwise direction through the annular chamber 15 and across the tube bundles in its path, its temperature is gradually lowered and the water or steam flowing within the tubes of the bundles successively encountered absorbs proportionately less heat. Accordingly, a tube bundle 25a positioned adjacent the perforated baifle 23 and spaced therefrom in a counterclockwise direction (FIGS. 2 and 3), encounters gas at the highest possible temperature, and is theerfore designated the super-heater tube bundle. The remaining three tube bundles 25b, 25c and 25d, which are sequentially arranged in a counterclockwise direction and are circumferentially spaced within the chamber 15 from one another and from the tube bundle 25a, are designated reheater, evaporator and economizer tube bundles respectively.

As water or steam flows through the tube bundles from the inlet headers to the outlet headers, heat exchange between the high temperature gas and the fluid to be heated is accomplished by the circular cross-flow of the respective fluids, the direction of flow of the water or steam being either vertically upwardly or vertically downwardly and the gas flow being circular.

Referring now to FIGURE 5, there is illustrated an alternative header arrangement 83- comprising spherical distribution headers 85 and vertical risers 87. The tube ends enter and are secured to the lower hemisphere of the headers and depend therefrom to form a bundle of rectangular cross-section. The riser 87 passes through the top head 29 and is welded thereto to form a gas-tight seal. The spherical header requires less material for a given volume, and material of a reduced thickness may be used as compared to the cylindrical header for the same pressure range application.

To further improve the circular flow characteristics of the gas flowing through the annular flow chamber 15, an alternative embodiment is shown in FIGURE 4 which includes a perforated baffle 89 similar to perforated baffle 23 and provided with a plurality of orifices 91 similar to the orifices 55. The baffle 89 is placed adjacent the outlet port 19 opposite the gas-impervious bafiie 21. Accordingly, the outlet port 19 is bordered on opposite sides by the bafiles which thereby define a vertical outlet passageway 9' In the alternate embodiment, the .gas flows through the annular chamber 15 and passes into the outlet passageway 93 at vertically spaced points therealong through the orifices 91 and thereafter flows vertically upwardly through the passageway 93 and out the port 19 into the top head 29.

As can 'be appreciated, a steam generator particularly adapted for use with a high temperature gas cooled nuclear reactor has ben provided which accomplishes heat exchange from the high temperature gas to the fluid to be heated through circular cross-flow of fluids, and incorporates either cylindrical or spherical headers in the water/ steam fluid system of the generator. This arrangement provides for compact construction, efficient heat transfer between the fluids and requiring a minimum amount of work to circulate the heated gas.

Various of the features of the invention are set forth in the following claims.

What is claimed is:

1. A stream generator comprising an outer containment shell having a vertically elongated cylindrical side wall, a top head and a bottom head, a vessel defining an elongated vertically disposed chamber of annular crosssection closed at opposite ends concentrically positioned within the space defined by said cylindrical side wall of said shell, said annular chamber being of a reduced diameter as compared to said cylindrical side wall and forming therebetween an annular vertically elongated passageway, a vertically elongated gas-impervious bafile plate within said vessel extending transversely across said annular chamber, a vertically elongated perforated baffle plate adjacent one side of said gas-impervious baffle plate, circumferentially spaced therefrom and forming therewith an inlet passageway within said chamber on one side of said gas-impervious bafile adapted to be connected to a source of pre-heated gas through the lower end of said chamber, said perforated bafile plate defining a plurality of vertically spaced orifices providing communication between said inlet passageway and said annular chamber, means defining an outlet opening in the upper end of said chamber adjacent the opposite side of said impervious bafile through which the gas may be discharged from said chamber into the space defined by said top head, the relative positions of said inlet passageway and said outlet causing the gas to travel in a general circular path through said chamber from said inlet orifices to said outlet opening, said annular chamber defining vessel additional defining a cylindrical passageway concentric with said chamber and interiorly located with respect thereto communicating between said top head and said bottom head adapted to cause said gas to flow downwardly therethrough into said bottom head, said annular passageway defined by said cylindrical side wall and said annular chamber also being in communication with said top and bottom heads whereby a portion of said gas is caused to travel therethrough to cool said shell, means defining an annular discharge passage connected to the lower end of said bottom head whereby said gas may be caused to discharge from said shell, and at least two vertically disposed horizontally spaced tube bundles adapted to transport the fluid to be heated, said tube bundles being disposed in said path of circular gas flow within said annular chamber.

2. A steam generator comprising an outer containment shell having a vertically elongated cylindrical side wall, a top head and a bottom head, a vessel defining an elongated vertically disposed chamber of annular cross-section closed at opposite ends concentrically positioned within the space defined by said cylindrical side wall of said shell, said annular chamber being of a reduced diameter as compared to said cylindrical side wall and forming therebetween an annular vertically elongated passageway, a vertically elongated gas-impervious baffle plate within said vessel extending transversely across said annular chamber, a first vertically elongated perforated baffle plate adjacent one side of said gas-impervious baffie plate, circumferentially spaced therefrom and forming therewith an inlet passageway within said chamber on one side of said gas-impervious baflie adapted to be connected to a source of pre-heated gas through the lower end of said chamber, said perforated baffle plate defining a plurality of vertically spaced orifices providing communication between said inlet passageway and said annular chamber, a second vertically elongated perforated baflle plate adjacent the opposite side of said gasimpervious bafile plate circumferentially spaced there- G from and forming therewith an outlet passageway within said chamber on said opposite side of said gas-impervious baffle adapted to discharge the gas from said chamber through the opposite end thereof into the space defined by said top head, said perforated baflie plate defining a plurality of vertically spaced orifices providing communication between said outlet passageway and said annular chamber, the relative positions of said inlet passageway and said outlet passageway causing the gas to travel in a generally circular path through said chamber from said inlet orifices to said outlet orifices, said annular chamber defining vessel additionally defining a cylindrical passageway concentric with said chamber and interiorly located with respect thereto communicating between said top head and said bottom head adapted to cause said gas to How downwardly therethrough into said bottom-head, said annular passageway defined by said cylindrical side wall andsaid annular chamber also being in communication with said top and bottom heads whereby a portion of said gas is caused to travel there through to cool said shell, and means defining an annular discharge passage connected to the lower end of said bottom head whereby said gas may be caused to discharge from said shell, and at least two vertically disposed horizontally spaced tube bundles adapted to transport the fluid to be heated, said tube bundles being disposed in said path of circular gas flow within said annular chamher.

3. A steam generator including in combination, a vessel comprised of an axially elongated cylindrical outer wall and an axially elongated cylindrical inner wall centrally of said outer wall, said vessel further comprising first and second end walls closing the space between said inner and outer walls at the ends thereof to define an annular elongated chamber, an elongated gas-impervious baffle plate within said chamber extending between said first and second end walls and transversely between said inner and outer walls, an elongated perforated baffle plate within said chamber extending between said first and second end walls and transversely between said inner and outer walls, said perforated baffle plate being circumferentially spaced from said gas-impervious bafiie plate and forming therewith an inlet passageway within said chamber on one side of said gas-impervious bafile plate, said first end wall having an inlet opening therein communicating with said passageway and adapted to be connected to a source of preheated gas, said perforated baffle plate having a plurality of axially spaced orifices therein providing communication between said inlet passageway and said annular chamber, said second end wall having an outlet opening on the side of said gas-impervious baflle plate opposite from said inlet opening and through which the gas may be discharged from said chamber, the relative positions of said inlet and said outlet openings causing the gas to travel in a generally circular path through said chamber from said orifices to said outlet opening, heat exchanger means located in the path of circular gas flow within said chamber, and casing means enclosing said vessel, said casing means cooperating with said outlet opening to direct the flow of gas discharged therethrough externally of said chamber to the first end wall thereof.

4. A steam generator including in combination, a vessel comprised of an axially elongated cylindrical outer wall and an axially elongated cylindrical inner wall centrally of said outer wall, said vessel further comprising first and second end walls closing the space between said inner and outer walls at the ends thereof to define an annular elongated chamber, an elongated gas-impervious bafile plate within said chamber extending between said first and second end walls and transversely between said inner and outer walls, an elongated perforated bafile plate within said chamber extending between said first and second end walls and transversely between said inner and outer walls, said perforated bafiie plate being circumferentially spaced from said gas-impervious baffle plate and forming therewith an inlet passageway within said chamber on one side of said gas-impervious bafil-e plate, said first end wall having an inlet opening therein communicating with said passageway and adapted to be connected to a source of preheated gas, said perforated baflle plate having a plurality of axially spaced orifices therein providing communication between said inlet passageway and said annular chamber, said second end wall having an outlet opening on the side of said gas-impervious bafile plate opposite from said inlet opening and through which the gas maybe discharged from said chamber, the relative positions of said inlet and said outlet openings causing the gas to travel in a generally circular path through said chamber from said orifices to said outlet opening, heat exchanger means located in the path of circular gas flow within said chamber, and means adjacent said outlet opening and cooperating therewith to direct the flow of gas discharged through said outlet opening centrally of said inner wall such that said inner wall defines a return passage for the gas externally of said chamber to the first end wall thereof.

5. A steam generator according to claim 3 including a second elongated perforated bafile plate within said chamber extending between said first and second end walls and transversely between said inner and outer walls, said perforated baffle plate being circumferentially spaced from said gas-impervious baflle plate on the side opposite from said first perforated baflle plate and forming with said gas-impervious baffle plate an outlet passageway comunicating with said outlet opening and adapted to discharge the gas from said chamber.

6. A steam generator according to claim 3 wherein the perforations in said perforated baffle plate vary in size to provide uniform flow of gas through all portions of the baffle plate.

References Cited by the Examiner UNITED STATES PATENTS 1,833,871 11/1931 Ewing et al. l160 2,567,695 9/1951 Cox l22-240 2,714,878 8/1955 Mekler 122235 2,944,532 7/1960 Frisch et a1. 122235 FOREIGN PATENTS 718,161 1/1932 France. 1,122,105 9/1956 France.

841,800 7/1960 Great Britain.

48,308 4/ 1940 Netherlands.

KENNETH W. SPRAGUE, Primary Examiner. D. G. BLACKHURST, Assistant Examiner. 

1. A STREAM GENERATOR COMPRISING AN OUTER CONTAINMENT SHELL HAVING A VERTICALLY ELONGATED CYLINDRICAL SIDE WALL, A TOP HEAD AND A BOTTOM HEAD, A VESSEL DEFINING AN ELONGATED VERTICALLY DISPOSED CHAMBER OF ANNULAR CROSSSECTION CLOSED AT OPPOSITE ENDS CONCENTRICALLY POSITIONED WITHIN THE SPACE DEFINED BY SAID CYLINDRICAL SIDE WALL OF SAID SHELL, SAID ANNULAR CHAMBER BEING OF A REDUCED DIAMETER AS COMPARED TO SAID CYLINDRICAL SIDE WALL AND FORMING THEREBETWEEN AN ANNULAR VERTICALLY ELONGATED PASSAGEWAY, A VERTICALLY ELONGATED GAS-IMPERVIOUS BAFFLE PLATE WITHIN SAID VESSEL EXTENDING TRANSVERSELY ACROSS SAID ANNULAR CHAMBER, A VERTICALLY ELONGATED PERFORATED BAFFLE PLATE ADJACENT ONE SIDE OF SAID GAS-IMPERVIOUS BAFFLE PLATE, CIRCUMFERENTIALLY SPACED THEREFROM AND FORMING THEREWITH AN INLET PASSAGEWAY WITHIN SAID CHAMBER ON ONE SIDE OF SAID GAS-IMPERVIOUS BAFFLE ADAPTED TO BE CONNECTED TO A SOURCE OF PRE-HEATED GAS THROUGH THE LOWER END OF SAID CHAMBER, SAID PERFORATED BAFFLE PLATE DEFINING A PLURALITY OF VERTICALLY SPACED ORIFICES PROVIDING COMMUNICATION BETWEEN SAID INLET PASSAGEWAY AND SAID ANNULAR CHAMBER, MEANS DEFINING AN OUTLET OPENING IN THE UPPER END OF SAID CHAMBER ADJACENT THE OPPOSITE SIDE OF SAID IMPERVIOUS BAFFLE THROUGH WHICH THE GAS MAY BE DISCHARGED FROM SAID CHAMBER INTO THE SPACE DEFINED BY SAID TOP HEAD, THE RELATIVE POSITIONS OF SAID INLET PASSAGEWAY AND SAID OUTLET CAUSING THE GAS TO TRAVEL IN A GENERAL CIRCULAR PATH THROUGH SAID CHAMBER FROM SAID INLET ORIFICES TO SAID OUTLET OPENING, SAID ANNULAR CHAMBER DEFINING VESSEL ADDITIONAL DEFINING A CYLINDRICAL PASSAGEWAY CONCENTRIC WITH SAID CHAMBER AND INTERIORLY LOCATED WITH RESPECT THERETO COMMUNI- 